I will take the liberty of reproducing the bits in which Messrs. Dreher and Longenecker quote the scientific results which they find most exciting. From Mr Dreher:

The one artifact in the book that really cannot be explained satisfactorily is the Shroud of Turin. Watch a CNN clip about it here. Gibson and McKinley write that the 1988 radiocarbon tests that demonstrated the Shroud was a medieval fake turned out to have been made not from the original shroud, but by an edge that had been patched onto the shroud in the 14th century. “Subsequent experiments cast further doubts on a medieval origin for the burial cloth,” they write.

Then, in recent years, the pace of revelations picked up. In 2011, scientists at Italy’s National Agency for New Technologies, Energy, and Sustainable Economic Development found that the markings on the shroud could have been created only by a “blinding flash of light.” Other, new experiments detected the ancient version of a “death certificate” on the shroud, while a recent study showed that the blood patterns on this “Man of Sorrows” indicated he was crucified on a Y-shaped cross — not the traditional T-shaped one that is the central icon of Christian art, and so central to Western civilization.

The authors say that “of all the Jesus relics in existence, [the shroud] is the best documented.” We know that the existence of a shroud-like burial cloth for Jesus is written about in the Gospels, having been purchased by Joseph of Arimathea. Jewish burial practices of the day are consistent with the image of the man on the shroud. Shroud debunkers allege that it was not mentioned in writings until the Middle Ages, but that is not true. St. Jerome writes about it in the fourth century. There is other historical evidence that Christians in the early church were aware of the shroud, and written accounts of it being displayed in the Christian East. Evidence strongly suggests turned up in medieval France as Crusader loot after Western Christian armies sacked Constantinople. In 1207, the authors write, a Catholic translator for the newly seated Latin patriarch of Athens wrote about how French knights robbed “the treasury of the Great Palace, where the holy objects had been kept,” and how he personally saw, with his own eyes, the burial linens of Jesus.

Scientifically, the tests on the shroud have produced remarkable results. Detailed analysis of the image showed that there is a three-dimensional quality to it, not observable to the naked eye, and that could not have been produced by painting. The stains on the shroud come not from paint, but human blood, and their patterning indicate that the man of the shroud suffered a savage flogging consistent with what the Gospels say Jesus endured before crucifixion.

The shroud depicts a crucifixion victim nailed to the cross through his wrists — this, even though Christian art shows Jesus nailed through his hands. We now know that the crucified had to have been nailed through their wrists, because nailing them through their hands would have been insufficient to support the weight of the body on the cross.

Scientists have found pollen on the shroud that can only have come from plants around Jerusalem — plants in bloom in the spring, in the season of Passover, when Jesus died. Particles from limestone tombs found in the Jerusalem area were discovered embedded in the shroud. More recently, detailed medical analysis confirms that the man of the shroud suffered precisely what the Gospels say Jesus suffered.

And then there is the matter of the Sudarium of Oviedo. I knew that the Sudarium existed, but I did not know until reading Finding Jesus that it had been used to validate claims for the Turin shroud as the burial cloth of the Nazarene.

From Mr Longenecker:

After my visit I am more convinced than ever not only that the Shroud of Turin is the burial cloth of Christ, but that the mysterious image was produced by a blast of radiance from the resurrection. Those who wish to research the shroud can find scholarly and popular articles here and here. The most interesting thing about the shroud is the more scientific research is done the more the claims to authenticity accumulate. Not only is the image on the shroud that of a crucified man, but a particular crucified man.

He wore a crown of thorns. His legs were not broken. His face was punched. His side was pierced in a way consistent with a Roman spear. His back shows the marks of a severe flogging consistent with the flagellum used by the Romans. In other words, all the wounds match those not just of any crucified man, but those unique to Jesus of Nazareth.

Other details match in an extraordinary way. Fabric experts acknowledge that the particular linen cloth matches that used in the first century by wealthy individuals. The chemical traces on the cloth match the herbs and spices that were known to be used for Jewish burials in Roman times. Pollen from the shroud matches that present in Jerusalem in the first century. New scientific dating techniques counter the 1988 carbon 14 dating which identified a medieval date and they date the shroud to the first century.

Most mysterious is the image itself. In 1978 a team of American researchers were finally given access to the shroud. They ran a whole series of tests covering the range of scientific disciplines. Their analyses found no sign of artificial pigments and they concluded, “The Shroud image is that of a real human form of a scourged, crucified man. It is not the product of an artist.” What formed the image? The scientists were stumped and admitted that “no combination of physical, chemical, biological or medical circumstances” could adequately account for the image.

Di Lazzaro and his colleagues at Italy’s National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) experimented for five years, using modern excimer lasers to train short bursts of ultraviolet light on raw linen, in an effort to simulate the image’s coloration.So what formed the image? The best description is that it is an extremely delicate singe marking. Italian physicist Paolo Di Lazzaro concedes in an article for National Geographic that every scientific attempt to replicate it in a lab has failed. “Its precise hue is highly unusual, and the color’s penetration into the fabric is extremely thin, less than 0.7 micrometers (0.000028 inches), one-thirtieth the diameter of an individual fiber in a single 200-fiber linen thread.”

They came tantalizingly close to replicating the image’s distinctive color on a few square centimeters of fabric. However, they were unable to match all the physical and chemical characteristics of the shroud image, and reproducing a whole human figure was far beyond them. De Lazzaro explained that the ultraviolet light necessary to reproduce the image of the crucified man “exceeds the maximum power released by all ultraviolet light sources available today.” The time for such a burst would be shorter than one forty-billionth of a second, and the intensity of the ultra violet light would have to be around several billion watts.”

The scientists shrug and say the only explanation lies beyond the realm of twenty-first century technoscience. In other words, the extraordinary burst of ultra violet light is not only beyond the ability and technology of a medieval forger. It is beyond the ability and technology of the best twenty-first century scientists.

What could explain all of this? If no known technological process could have produced the image on the shroud, and the only unknown technological processes that could have produced it would be the result either of the greatest design fluke in history or of contact with visitors from outer space, perhaps we should discard the forgery hypothesis and turn next to a search for a natural process that could have produced the image. There may in fact be such a process. Lightning is an extremely energetic and poorly understood phenomenon; it was only in 2009 that it was discovered that lightning often produces significant amounts of antimatter in the upper atmosphere. No one had expected to find this, and no one can explain it. Bursts of ultraviolet radiation are a lot less exotic than appearances of antimatter, and so would be significantly less surprising as phenomena associated with lightning.

So, perhaps at some point in the middle decades of the first century CE in or near the city of Jerusalem the body of a man who had been scourged, jabbed in the side with a spear, mounted on a cross, fastened to that cross with nails through his wrists and feet, and subjected to a group of small puncture wounds on the forehead was wrapped in the shroud that has been on display in Turin for the last several centuries. Before that man’s body was buried or entombed, it was struck by lightning, producing a burst of ultraviolet rays that created the image on the shroud. This event, occurring in an urban area and centering on the body of a man whose gruesome death a crowd would have witnessed at most a few hours before, would certainly have been very much discussed. One must suppose that people would try to find religious significance in it, and that in the course of those discussions many people would claim, whether truthfully or not, to have been associated with the man during his lifetime.

Perhaps the whole story of Jesus, as it has come down to us, grew from the reactions to this event. Or perhaps the story of Jesus as we have it represents the conflation of several stories. It is difficult to imagine that the man whose image is preserved in the shroud is not the man whose crucifixion is described in the Gospels, but not so difficult to imagine that stories about another man, who was also crucified in Jerusalem around the same time and who was well-known locally before his crucifixion as the leader of a new religious movement, would be combined with the story of the man whose crucifixion was followed by the spectacular event of a lightning bolt and the transformation of his burial cloth into the object we now see in Turin.

Nowhere in the New Testament does it say that Jesus’ body was struck by lightning after it was removed from the cross. If the image on the shroud turns out to have been created by lightning, the evidence connecting it with first-century Jerusalem, the fact that its appearance in first-century Jerusalem would certainly have caused great excitement there, and the similarity of the wounds the man had to the wounds the Gospels attribute to Jesus makes that silence a tremendous obstacle to accepting the historicity of the Gospels, I would say a far bigger obstacle than any of the gaps or discrepancies of detail that New Testament scholars have yet uncovered.

All the other problems fade pretty quickly once you start thinking of the Gospels as what they originally were, a collection of liturgical resources more akin to a hymnal than to a biographical study. The Gospels are series of pericopes, distinct passages designed to be read aloud or recited at particular moments in worship services. No doubt these pericopes took shape gradually in the worship services Christians conducted in the decades between Jesus’ death and the production of the first written versions of the Gospels. It is hardly surprising that the Gospels diverge in various details and leave out many things a modern reader might like to know. To the extent that those divergences and gaps show us anything, they show us only that there are certain things we care about that the late first century Church didn’t care about at all and that the fourth century Church didn’t care about sufficiently to do anything about them at the First Council of Nicaea (325 CE.)

However, if the body of the man whose crucifixion was described in the Gospels was struck by lightning before it could be buried or entombed, and if that lightning strike created the image we see on the Shroud of Turin, that is something we can be sure everyone in Jerusalem would have cared about and would have talked about for years. If that did happen and it isn’t recorded or even hinted at anywhere in the New Testament, we must ask whether any of the authors of the New Testament had any connection with Jesus at all, and if not whether their accounts are reliable at any point. Surely anyone who was in Jerusalem that day, or who had talked about the events of the day with people who were there, would have known about such an extraordinary occurrence. And surely anyone who goes to the lengths the authors of the New Testament do to stress the point that extraordinary occurrences tended to happen when Jesus was around would have been highly motivated to make note of it had a lightning strike hit his body and emblazoned his image on his shroud. If the Gospels and the liturgies for which they were prepared grew up among people who were so remote from Jesus and his inner circle that such an event could have taken place without their knowledge, then there isn’t much left for Christians to believe.

So, for Christians, there seems to be a great deal at stake in the question of what precisely the Shroud of Turin is. If the recent studies of it are all wrong, if the researchers have been led astray by their religious biases and it is after all a forgery from the Middle Ages, then the crisis is averted. If the studies hold up, and if the image does prove to be the result of a lightning strike, do Christians have a way out?

Maybe they do. I can think of two reasons why something so important might deliberately be left out of the New Testament. First, it could be that the Church, subject as it was to persecution, did not want to attract its enemies’ attention to the existence of so precious a relic. Second, since the shroud is a single object, it must be kept in a single location owned by a single authority. Yet by the time of the very earliest writings in the New Testament, the Church was already composed of multiple autonomous groups bound together by goodwill and the habit of imitation rather than a unity of command-and-control structures (see 1 Thessalonians 2:17-3:3,) and the Gospels explicitly state that Jesus endorsed this decentralized organizational model (Mark 9:30-39, Luke 9:46-50.)* Whichever group had the shroud in its possession would be in a unique position to claim to be The Church, as indeed the Roman Catholic Church has for some time been pleased to do. So, other groups would be leery of such claims, and the group that had safekeeping of the shroud would be tactless to make too much of that fact. A document originating from a group other than the one that had custody of the shroud would therefore be unlikely to call its own authority into question by dwelling on the shroud, while a document originating from the group that did have custody of it, if the group meant to invite other, independent groups to make liturgical use of the document, would not be much likelier to dwell on it.

If the shroud is the shroud of someone else, and it is simply a fantastic coincidence that the body of another man, crucified in the same city in the same century with the same wounds as Jesus was struck by lightning and that that lightning created the image we see on the Shroud of Turin, then I believe Christians must hope that someday a scrap of paper will surface from some lost first-century document mentioning that coincidence, and saying that people marveled at the fact that in one city in one lifetime two crucified men were the center of fantastic events that took place after their deaths. Perhaps such a hypothetical scrap would go on to say that the shroud had fallen into the hands of some gang of heretics who were using it to prop up their claim to be The Church, and that orthodox Christians, embarrassed by this gross blasphemy, tried to pass it over in silence. Failing the appearance of such a scrap, if we should learn that the shroud was someone else’s, it is hard to avoid the suspicion that the crucifixion stories in the Gospels are retellings of that man’s crucifixion, not the crucifixion of Jesus. In that case, everything about Jesus before and after the crucifixion narratives would also fall to pieces.

Now, this idea of mine about lightning is just a hypothesis. Subsequent examination may prove that a lightning strike could not have caused the image to appear. Tests may also confirm the results that seem to rule out a forgery. And our knowledge of nature may advance to the point where we can be confident that no other natural phenomenon could have produced the image. Should that day come, we would be left to choose between, on the one hand, a miraculous explanation such as a burst of ultraviolet radiation accompanying the Resurrection, and on the other a science-fiction explanation involving either incautious visitors from outer space or mischievous time travelers from the far future. We aren’t there yet, and devotees of the Shroud of Turin should be aware that the road that may someday lead us there may also, for all science can now tell us, lead us to the very last place they would ever want us to find ourselves.

*Matthew 7:22-23 limits the application of these verses to the ecclesiological question by excluding them from the question of salvation. That is to say, the fact that people welcome the lowly and cast out demons in Jesus’ name shows that their acts are the acts of the Church, but it does not by itself show that those people will not ultimately be damned.